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C. A. RANDALL.

Chemical Telegraph.

No. 237,595. 59, Patented-Feb..8, 1881.

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A TTORNEY NFETERS, PHOTO-LITHOGRAPHER. WASHINGTON D C UNITED STATES 'A'rENT Fries.

CHARLES A. RANDALL, OF NEW YORK, N. Y.

CHEMICAL TELEGRAPH.

SPECIFICATION forming part of Letters Patent No. 237,595, dated February 8, 1881.

Application filed June 18, 1880.

To all whom it may concern Be it known that I, CHARLES A. RANDALL, of the city, county, and State of New York, have invented certain new and useful 1m- 5 provements in Chemical-Telegraph Systems and Apparatus, of which the following is a specification.

My invention relates to that class of chemical telegraphs'in which the transmission is ef- Io fected by an automatically-operating transmitter, through the agency of a perforated strip of paper or other non-conducting material previously prepared for that purpose, the communication being recorded at the receiving-station by the discoloration of chemicallyprepared paper in a well-known manner.

My improvement consists, first, in a method of transmitting signals composed of alternate positive and negative electric currents or impulses, which method consists in producing the necessary alternation of currents by means of a continuously-operating pole-changer and controlling the transmission of the alternate currents over the line by means of a moving 2 5 perforated band of non-conducting material, whereby the reversal of the current is effected independently of the action of the perforated transmitting-strip; second, in a method of transmitting signals composed of alternate 0 positive and negative electric currents or impulses, which method consists in transmitting two or more impulses, either of like or of unlike polarity, from a single perforation in a band of non-conducting material; third, in

3 5 the combination of a pole-changer or commutator for transmitting alternate positive and negative electric currents or impulses with a make-and-break or non-reversin g transmitter included in the same circuit, and with suita-- 4o ble mechanical devices for maintaining a constant and uniforinrelation between the movements of the pole-changer and the transmitter, whereby they are made to act in conjunction with each other to produce the required I 4 5 succession of signals upon the line; fourth, in

the combination of a pole-changer or commutator fortransmitting alternate positive and negative electric currents or impulses with a moving perforated band of non-conducting 5o material having a determinate rate of motion relatively to the motion of the pole-changer, whereby perforations in the band may be so (No model.)

arranged, in groups or otherwise, that when said band is put in motion to close and break the circuit of the main line it shall act, in conjunction with the commutator, to produce the alternation and succession of impulses upon the line required to record the corresponding signals at the receiving-station; fifth, in the combination of a pole-changer or commutator, so constructed as to transmit alternate positive and negative impulses which shall be equal to each other in length or duration, with a moving perforated band of nonconducting material having single perforations for transmittin g signals representing dots, and groups of perforations for transmitting signals representing dashes. In the accompanying drawings, Figure l is a plan View of an automatic transmitting apparatus embodying my improvements. Fig. 2 is a vertical transverse section of the same. Fig. 3 is a representation of a section of the perforated transmitting band or strip, and Fig. 4 is a representation of a similar section of the strip of paper containing the corresponding signals as they appear when recorded.

The machinery of the transmitter is inclosed between two metallic side plates or frames, B B, which are secured to a base, A. The main arbor O is mounted in suitable bearings, so as to be capable of revolving freely,and carries a pulley, c, a metallic drum, D, and a toothed wheel, 01. The arbor O is to be driven in the direction of the arrow in Fig. 2 by a strap or band passing over the pulley c and connected with any suitable or convenient source of power. A strip or band of paper or other suitable non-conducting material, K, passes over the metal drum D, and is drawn along at a uniform rate by its revolution, or by special devices which may be applied for that purpose-as, for example, additional pairs of rollers geared to the same axis, the construction and arrangement of which are well understood and need no particular description. A metallic brush, H, composed of a row of metallic wires placed side by side and secured in a holder, h, presses upon the band K directly over the drum. D, as best seen in Fig. 2, by virtue of its own resiliency. The brush-holder h is secured by an adjustable screw or other similar device to the post h on the base A, which arrangement admits of the adjustment of the pressure of the teeth of the brush H upon the moving band K. The band K is perforated with circular holes k 7; 7a, Fig. 3, at varying intervals, as hereinafter explained, by means of suitable and well-known machinery adapted to the purpose. As these perforations successively pass under the brush If its teeth drop through them and make an electrical contact with the drum D beneath the perforated strip. The apparatus thus constitutes an automatic make-and-break transmitter.

The toothed wheel d drives a. pinion, 0, upon a second arbor, E, parallel to the arbor 0, upon which is mounted a reversing-commutator or pole-changer. This may be of the ordinary form, as shown in the drawings, consisting of a cylinder of non-conductin g material, F, which serves as an insulating-couplin g to connect together the two parts of the metallic arbor E, (these being electrically separated from each other,) and also as a support for the two disks f and f, which are each constructed one half of conducting and one-half of non-conductin g material, as shown in Figs. 1 and 2. Theconducting portion off is connected with one end of the arbor E and that of f with the other end. The contact-springs g and g, which are connected with the positive and negative poles, respectively, of a battery, I, rest upon the peripheries of the disks f and f of the commutator as they revolve. The battery I is connected with the earth at G by a wire proceeding from a point not far from midway between its poles. The effect of this arrangement is as follows: \Nhen the arbor E revolves, during one-half of its revolution a current is sent from the positive pole of the battery I through the frame B, the drum D, and the brush H, to the line at L, while during the other half of its revolution a similar current is sent from the negative pole, the main line being constantly closed at the commutator. If, therefore, the circuitis complete through one of the perforations in the strip K, the brush H being in contact with the drum D, a rapid and continuous succession of alternate positive and negative impulses would be sent to the line by the rotation of the commutator upon the arbor E. I prefer to so proportion the mechanism connecting the two arbors O and E that during the time that one perforation, as k, is passing under the brush Hthe commutator shall transmit four pulsations--two positive and two negativefor reasons hereinafter stated. It is obvious that this proportion must necessarily be maintained during the operation of the apparatus, irrespective of the absolute rate of speed at which the apparatus is made to revolve.

The result which the apparatus is designed to accomplish is to automatically transmit currents which shall produce signs consisting of combinations of dots and lines by the discoloration of chemical paper at the receiving-station, as shown in Fig. 4., which exhibits a portion of the record corresponding to the perforated strip in Fig. 3. It is well known that the marks will be only produced by the action of the current from the positive pole of the battery, and not by that from the negative, audit has therefore been customary in apparatus of this kind to transmit currents by a make-andbrcak transmitter from the positive pole of the battery only. A serious difficulty at once presented itself in connection with this mode of transmission, inasmuch as the inductive capacity of the line-wire caused it to retain a small portion of the electricity at the termination of each impulse, which continued to flow to the earth through the recording-instrument after the circuit was broken,thus filling up the space between the successive signs and rendering them partially or wholly illegible inv case the line was of great length or the succession of signals rapid. This residual or inductive current may, however, be neutralized or destroyed by sending a current of reverse polarity at the termination of each signal. 1 will now explain the method which I employ for accomplishing this result by means of the apparatus which has been described.

Referring to Fig. 4, the first character on the paper strip represents the letter A, and consists of a short line, technically called a dot, at, a space of the same length, 0, and finally a line of twice the length of m, termed a dash, n. This is followed by a space of double length, 12, which serves to separate the letter from the succeeding one. In order to produce this character the perforations in the strip K, Fig. 3, are grouped as follows: A single perforation, 70, corresponds to the dot, a space, 8, equal to one perforation to the space 0, two perforations close together, k, to the dash n, and a space, 8, equal to two perforations to the space 1).

The operation is as follows: While the perforation 7." is passing under the brush H four impulses go to line in the following order: positive, negative, positive, negative. As the positive portion of the battery is by preference adjusted so as to be of greater power than the negative it does not entirely destroy the residual current before the arrival of the second positive current; but this latter being followed by another negative current and then by a space, the second negative current acts uninruptedly long enough to effect a complete neutralization and to discharge the line. The result is that the first positive current and the second one are blended together upon the recording-instrument and form a single dot, m, while the second one is cut oif sharply by the negative impulse and forms a space, 0. The dash n and space 1) are formed upon the same principle. It is obvious that the same effect in theory could be produced by sending only two impulses, a positive followed by a nega tive, from each perforation; but I prefer to arrange the apparatus to send a greater number, as a betterresultin practice is thereby attained.

The relative efiective strength of the positive IIO and negative portions of the battery I is adjusted by changing the point of connection of the ground-wire G from point to point in the series of cells. The portion which transmits the positive current should, however, be always in excess, the proportion depending upon the condition of the line and other circumstances, the proper adjustment of the two parts being determined experimentally upon observing the distinctness of the record at the receiving-station.

I do not desire to confine myself to the particular apparatus which I have shown for carrying out the principles of my invention, as the arrangement of the commutator, for example, may be varied in many ways, or other devices substituted for the perforated paper and brush for automatically making and breaking the circuit without departing from the spirit of the invention, as hereinbefore set forth.

I claim as my invention- 1. The hereinbefore-described art, method, or system of transmitting over a telegraphic circuit signals composed of alternate positive and negative electric currents or impulses, which consists in producing the required alternation of currents by means of a continuously-operating pole-changer, and controlling the transmission of the alternate currents over the line by means of a moving perforated band of non-conducting material.

2. The hereinbefore-described art, method, or system of transmitting over a telegraphic circuit signals composed of alternate positive and negative electric currents or impulses,

which consists in transmitting two or more impulses, either of like or unlike polarity, from a single perforation in a band of non-conducting material.

3. The combination, substantially as herein set forth, of a pole-changer for transmitting alternate positive and negative electric currents or impulses, a make-and-break transmitter included in the same circuit, and mechanism for maintaining a constant and uniform relation between the movements of the polechanger and the transmitter.

4. The combination, substantially as herein set forth, of a pole-changer for transmitting alternate positive and negative electric currents or impulses, with a moving perforated band of non-conducting material having a determinate rate of motion relatively to the motion of the pole-changer.

5. The combination, substantially as hereinbefore set forth, of a pole-changer constructed to transmit alternate positive and negative electric impulses of equal length or duration, with a moving perforated band of non-conducting material having single perforations for transmitting signals representing dots, and groups of perforations for transmitting signals representing dashes.

Signed by me this 12th day of June,A. D. 1880.

CHARLES A. RANDALL. Witnesses:

WM. 0. WITTER, MILLER O. EARL. 

